Smart cards are well known devices that include a card body into which is embedded an integrated circuit (IC) module. The integrated circuit module includes an integrated circuit chip that is designed to store data that can be used, inter alia, to provide the card with electronic identification, authentication, data storage and application processing capabilities. As a result, smart cards, which are also commonly referred to as integrated circuit cards or chip cards, are widely used in commerce to provide information and/or application processing capabilities in connection with, but not limited to, bank cards, credit cards, health insurance cards, driver's licenses, transportation cards, loyalty cards and membership cards.
Smart cards of the type as described above transmit data stored on the integrated circuit module using either (i) a direct contact interface (the resultant products being commonly referred to in the art as contact smart cards), (ii) a contact-free interface (the resultant products being commonly referred to in the art as contactless smart cards) or (ii) a hybrid of the two aforementioned interfaces (the resultant products being commonly referred to in the art as dual-interface smart cards).
Dual-interface smart cards utilize an integrated circuit module that is specifically designed to allow for the transmission of signals through either a direct contact or a contact-free interface, this type of module often being referred to in the art as a dual-interface IC module. Referring now to FIGS. 1(a) and 1(b), there are shown front and rear plan views, respectively, of a segment of an IC module reel 11 that includes a plurality of individual dual-interface IC modules 13 arranged in pairs in a side-by-side relationship, each module 13 being punched, or otherwise separated, from reel 11 upon completion of assembly. As can be appreciated, the fabrication of IC modules 13 from a continuous reel 11 greatly facilitates the manufacturing process.
Reel 11 comprises a module tape 15 that not only serves as the principal carrier for reel 11 but also serves as the substrate for each individual module 13. Tape 15 is a thin, continuous, ribbon-type strip constructed of a non-conductive material, such as a glass epoxy, that has a generally flat top surface 15-1 and a generally flat bottom surface 15-2.
As seen most clearly in FIGS. 1(a) and 2, top surface 15-1 of tape 15 is plated to define a plurality of separate contact pads 17-1 thru 17-8 within the footprint of each module 13, each contact pad 17 being constructed of a highly conductive material, such as gold-plated or nickel-plated copper. The particular size, shape and arrangement of contact pads 17 for each module 13 are largely defined by International Organization for Standardization (ISO) standards for the manufacture of smart cards and together provide a total surface area of approximately 1 square centimeter. In use, contact pads 17 enable each module 13 to interface with an appropriate card reader by means of direct contact, with certain contact pads 17 designated to transmit particular signal components (e.g. input/output signal, clock signal, power, etc.).
As seen most clearly in FIGS. 1(b) and 2, an integrated circuit chip 19 is mounted on bottom surface 15-2 by an adhesive 21 at the approximate midpoint within the footprint of each module 13. An arrangement of holes 23-1 thru 23-8 is punched transversely through tape 15 in a spaced-apart, circular arrangement around IC chip 19. It is to be understood that holes 23-1 thru 23-8 are specifically positioned to provide direct access to the underside of contact pads 17-1 thru 17-8, respectively. In this manner, a conductive wire (e.g. a gold-plated wire) 25 can be fed through each hole 23 and bonded, at its ends, to IC chip 19 and its corresponding contact pad 17 to establish an electrical path therebetween. As a result, data stored on IC chip 19 can be transmitted through wires 25, to selected contact pads 17 and ultimately received by a card reader (not shown) in contact therewith.
An encapsulation material, or encapsulant, 27 is commonly deposited as a generally semi-spherical mass over IC chip 19 as well as any wires 25. Encapsulant 27 is preferably constructed of a rigid and durable material, such as a hard epoxy resin, that serves to protect the relatively sensitive electrical components and ensure that adequate connectivity is maintained.
Additionally, bottom surface 15-2 of tape 15 is plated to define a pair of antenna contact pads 29-1 and 29-2 within the footprint of each module 13, each antenna contact pad 29 being constructed of a highly conductive material, such as gold-plated or nickel-plated copper. Antenna contact pads 29 are located on opposing sides of module 13 and are connected to IC chip 19 by corresponding conductive wires 31 to establish an electrical path therebetween.
As can be seen, each conductive wire 31 and a portion of its corresponding contact pad 29 are protected by encapsulant 27. At the same time, a portion of antenna contact pads 29 extends beyond the periphery of encapsulant 27 and is thereby rendered externally exposed for connection to an antenna embedded in the card body.
In use, the antenna provides non-contact means for transmitting communication signals between integrated circuit module 13 and an associated card reader. The antenna is commonly constructed as a conductive wire that is arranged in a coiled, or spiraled, configuration within the card body. Each free end of the wire is often arranged into a dense configuration, such as a tightly wrapped coil, spiral, W-shape, or zig-zag formation, to form a suitable contact terminal.
To achieve functionality of the smart card, the IC module needs to be coupled to the antenna. Traditionally, the integrated circuit module is connected to the antenna through either direct connection or inductive coupling.
Direct connection relies upon connecting a conductive element (e.g. a wire, conductive epoxy or combination thereof) between the antenna contact pads on the IC module and the contact terminals for the antenna. However, in order to directly connect the antenna contact pads on the IC module to the contact terminals of the antenna, a cavity is typically milled in the card body to a depth that is sufficient to at least partially expose the antenna contact terminals.
With the contact terminals for the antenna exposed, direct connection is commonly achieved between the antenna and the IC module using a variety of different connection techniques.
As an example, in U.S. Pat. No. 8,640,965 to C. M. Sutera, the disclosure of which is incorporated herein by reference, there is shown a dual-interface smart card that electrically connects an IC module to exposed sections of an antenna using a pair of opposing, stapled-shaped, conductive elements, with one conductive element being permanently welded to a contact pad on the IC module and the other conductive element being permanently welded to the antenna. Each conductive element includes a pair of resilient spring arms that maintain electrical connection between the contact pad and the antenna even upon movement of the IC module relative to the card body. To provide further redundancy of connection between each contact pad and the antenna, the resilient spring arms of the opposing conductive elements are encapsulated with a supply of conductive filler material.
As another example, in U.S. Pat. No. 6,881,605 to C. K. Lee, the disclosure of which is incorporated herein by reference, there is disclosed a method of forming a dual-interface smart card that establishes connection between an IC and an antenna coil by pulling out the two free ends of the antenna coil from the core sheet, and securing each of the extracted free ends of the antenna to the integrated circuit, for example, by soldering or thermocompression bonding.
As referenced above, dual-interface IC modules are conventionally constructed by plating both sides of the module tape, this type of module tape being referred to herein as having a double side plated module tape construction. By plating both sides of the module tape, the resultant IC module is provided with a first set of contact pads on its top surface that allow for direct contact signal transmission to an appropriate card reader and a second set of contact pads on its bottom surface that serve as points of connection between the IC module and an antenna embedded in the card body, the antenna allowing for contact-free signal transmission to an appropriate card reader.
Dual-interface IC modules that rely upon a double side plated module tape construction have been found to suffer from a notable drawback. Specifically, a significant number of processing steps (e.g. layer deposition, patterned light exposure, and chemical developing) and a substantial amount of materials are required in order to plate both sides of the module tape, resulting in an IC module that is relatively expensive to manufacture. In fact, dual-interface IC modules, which typically utilize a double side plated module tape construction, are often as much as 40% more expensive to manufacture than IC modules used in contact smart cards, which typically utilize a single side plated module tape construction.